The LinqDataSourceUpdateEventArgs object is passed to any event handler for the Updating event. You can use the LinqDataSourceUpdateEventArgs object to examine the data before the update operation is executed in the data source. You can then validate the data, examine validation exceptions thrown by the data class, or change a value before the update. You can also cancel the update operation.

The OriginalObject object contains the data that was originally retrieved from the data source. The NewObject object contains the data that will be saved in the data source during the update operation.

If the object that represents the data source throws a validation exception before updating the data, the Exception property contains an instance of the LinqDataSourceValidationException class. You can retrieve all the validation exceptions through the InnerExceptions property. If no validation exception is thrown, the Exception property contains a null reference (Nothing in Visual Basic). If you handle the validation exceptions and do not want the exception to be re-thrown, set the ExceptionHandled property to true.

By default, the LinqDataSource control stores the original values from the data source in view state on the Web page, except those whose ColumnAttribute attribute is marked as UpdateCheck.Never. LINQ to SQL automatically checks the integrity of the data before updating the data. It does this by comparing the current values in the data source with the original values stored in view state. LINQ to SQL raises an exception if the values in the data source have changed. You can perform additional data validation by creating a handler for the Updating event.

The following example shows an event handler for the Updating event. The example shows how to compare properties from the OriginalObject property and the NewObject property to determine whether the value in the Category property has changed. If so, the CategoryChanged property of the object in the NewObject property is set to true.